readpipe

EXPR is executed as a system command.
The collected standard output of the command is returned.
In scalar context, it comes back as a single (potentially
multi-line) string. In list context, returns a list of lines
(however you've defined lines with $/
or $INPUT_RECORD_SEPARATOR
).
This is the internal function implementing the qx/EXPR/
operator, but you can use it directly. The qx/EXPR/
operator is discussed in more detail in I/O Operators in perlop.
If EXPR is omitted, uses $_
.

perldoc.perl.org - Official documentation for the Perl programming language